How to Handle Water-Based Clay (so your sculpture doesn't explode)?

[l'Aria]

Hey guys! I recently finished my first clay bust. I've never sculpted anything before so I'm entirely new this medium. After spending several days sculpting and a little more than a week to dry, when I fired the sculpture, it exploded in the kiln

Judging by the way the pieces separated in the kiln, I figured it had something to do with the way I put the clay together. What's the best way of merging two layers of clay together? Scoring? Water to make the clay act as a glue? Hammering it down with a hard object?

I know the sculpture was too thick in some areas, so it may have still been wet inside when it was fired (which definitely could have contributed to what happened). However, I did have a hole at the base and hollowed out the head, so I know that wasn't the problem.

If you have any tips for me or maybe if you look at the image and see another problem that may have caused the bust to explode, I'd appreciate any bit of advice you have As you may have guessed, I have no idea what I'm doing haha

[b1938dc]

It is possible that the clay was contaminated.(air pockets, plaster, etc.) Or perhaps the clay was not dry all the way because in order to fire the clay it has to be bone dry all the way through where it is most brittle. If this was place outside in the sun it would dry the surface fast but leave the middle moist (This usually leads to cracking though). Scoring is not necessary, but it is usually used in ceramics where one might want to add a handle, spout, or to make a hollow sphere where a hole can be added later. Scoring is a means to add something without messing up what it is being attached and what it is being attached to so it can be used for sculpture but rarely though. Also, when adding clay, make sure that air pocket are not created.

I hope this helps.

[egerie]

Are you sure this clay could be used to be fired? Not all water clays can make a safe trip trough the kiln...

[l'Aria]

b1938dc: Ah I didn't even think about air pockets! It's certainly possible that they may have also been a cause since, like I mentioned before, I don't believe I put the layers as seamlessly together as I needed to. I'm not positive if remaining moisture could have been a cause; as far as I could tell, it was bone dry on the surface, but maybe the inside was still wet because of the thickness of the sculpture itself.

Thanks so much! Your post really helped me out!

egerie: haha yes, I'm sure. It's advertised as a firing clay

[Meloncov]

Letting a piece dry longer will cover for a lot of sins. A dry air pocket isn't likely to explode, but one with a bit of moisture will. Just be aware that, depending on climate and clay thickness, fully drying out a sculpture can easily take months.

[b1938dc]

You're welcome tempest-haze.

[philofmars]

[SIZE="1"]b1938dc: Ah I didn't even think about air pockets! It's certainly possible that they may have also been a cause since, like I mentioned before, I don't believe I put the layers as seamlessly together as I needed to. I'm not positive if remaining moisture could have been a cause

I took clay in HS and that was the single biggest problem with our stuff exploding. That's why you knead it, and knead it, and bang it, and throw it down, and knead it some more. If you look at the pieces you can almost always find the culprit. When joining pieces, make some "slip" (watered down mud) from the clay and use that between the pieces to make sure there is no air in the joint.
BTW: It looks like it went off like a bomb! I am sad for you, but wow. I never saw one explode so much. She was beautiful.

[l'Aria]

Meloncov: Wow, I didn't think it could take that long. Thank you for the advice. I'll be more patient with drying next time!

philofmars: Air bubbles can still exist within the clay even if you just cut it with a wire off the block it was shipped to you in? haha wow I have a lot to learn...
Aw, thank you! hahaha yeah I was lucky I could even save an ear! I was pretty upset too, namely because it's something I could have prevented had I known all of these things beforehand. But I still have pictures and the experience; I guess that's what counts in the end


I can't thank you guys enough for your advice. I feel confident I can make it work this time!

[philofmars]

Air bubbles can still exist within the clay even if you just cut it with a wire off the block it was shipped to you in? haha wow I have a lot to learn...

Not usually, but I don't think I have ever worked with clay not used by someone else.

read this.
http://www.ehow.com/info_8663920_pro...bles-clay.html

[l'Aria]

philofmars: Thanks for the link! I see what you mean now. Since I purchased my clay from Blick, I guess it's safe to say that the manufacturer already removed the air bubbles.

[sloopster]

you need to wedge your clay ... you cut your block into 2 and smooch it back together and keep kneeding it, any clay you get from a store will need to be wedged clay is genraly extruded into the container or bag you buy it in that process normaly forces air into it, that will cause your pot of sculpture to explode in the kiln. also if you make your sculpture hollow and leave a hole in it so that the air can curculate your sculpt will dry out quicker and be less likely to have issues with that.

[clifcarver]

No one mentioned the firing cycle.

The thicker your clay, the slower it should be warmed, and the longer it should remain in the lower temperatures. Especially in the first temperature rise to 225 degrees F, or so. For wall thickness greater than 1/2 inch, some sculptors will leave the work in the kiln, on low, overnight with the lid up.

For 1/4 to 1/2 inch clay wall, four hours at this temperature might do.

Also the burning off of organics is done more slowly for thicker clay wall and larger pieces. Slower raising and longer holding time at 500 F and 750 F. Peep holes open to allow moisture and odors to escape.

Playing with simple things can give experience, and avoid disappointment in more important work. You can learn a lot from books and web things on firing pottery in an electric kiln.